In the framework of the TMD factorisation and up to the order \(1/Q\)  (twist-three), the amplitudes can be interpreted as convolutions of TMD PDFs and TMD fragmentation functions (TMD FFs) over the intrinsic quark transverse momentum \(\mathbf {k_\mathrm {T}}\)  and the transverse momentum \(\mathbf {p_\perp }\)  obtained in the fragmentation [1]}:
\(A_\mathrm {UU}^{\cos \varphi _\mathrm {h}} = \frac{2M_\mathrm {p}}{Q} \frac{\mathcal {C}\biggl [-\frac{\mathbf {h}\cdot \mathbf {k_\mathrm {T}}}{M_\mathrm {p}} f_1 D_1- \frac{(\mathbf {h}\cdot \mathbf {p_\perp })k_\mathrm {T}^2}{M_\mathrm {p}^2 M_\mathrm {h}} h_1^\perp H_1^\perp + ...\biggr ]}{\mathcal {C}\bigl [ f_1 D_1\bigr ]},\quad A_\mathrm {UU}^{\cos 2\varphi _\mathrm {h}} = \frac{\mathcal {C}\biggl [-\frac{2(\mathbf {h}\cdot \mathbf {k_\mathrm {T}})(\mathbf {h}\cdot \mathbf {p_\perp }) - \mathbf {k_\mathrm {T}}\cdot \mathbf {p_\perp }}{zM_\mathrm {p}M_\mathrm {h}}h_1^\perp H_1^\perp \biggr ]}{\mathcal {C}\bigl [ f_1 D_1\bigr ]},\) 
